Mainframe computers are large scale computer system architectures that are used by large organizations for bulk data processing, such as financial transaction processing. Mainframe computers offer enhanced availability, scalability, reliability and security along with high volume data throughput, among other features. For example, IBM Corporation's System z is a mainframe platform and computing environment that is widely used in the industry and that includes z/Architecture-based systems and zSeries mainframes. System z components may operate with IBM's z/OS (operating system) and/or other zSeries operating systems. Input/Output (I/O) devices may be coupled to interact with mainframe computers, such as IBM's System z computing environment, that may include an I/O subsystem that communicates with the I/O devices over communication channels. The I/O subsystem controls data flow between I/O devices and main storage. The I/O subsystem may be coupled to the central processors of the main system and may communicate directly with the I/O devices. I/O subsystem may communicate with the I/O devices using multiple types of interfaces, including, for example, communication channels such as Fibre channels.
Software may be designed to emulate, and/or otherwise simulate, other programs, such as operating systems. For example, it may be desirable to emulate IBM's z/OS operating system using software. It is also possible to emulate, or and/or otherwise simulate, hardware systems, such as processors, used in connection with computing systems. For example, it may be desirable to emulate components of IBM's z/Architecture computing systems. Emulation of hardware and software systems may be useful in connection with testing and other operations of I/O devices and/or other software applications and hardware components that interface with a computing environment, such as IBM's System z. One reason, in particular, for emulation is that the cost of running a System z environment may be significant. For further discussion of z/OS and z/Architecture components, see, for example, Loveland, et al., “Testing z/OS: The premier operating system for IBM's zSeries server,” IBM Systems Journal, Vol. 41, No. 1, 2002, pp. 55-73, and Plambeck, et al., “Development and attributes of z/Architecture,” IBM J. Res. & Dev., Vol. 46, No. 4/5, July/September 2002, pp, 367-379, which are incorporated herein by reference. See also, z/Architecture: Principles of Operation, IBM, SA22-7832-04, 2005 for a detailed z/Architecture description.